Sap flow response to olive water stress: a comparative study with trunk diameter variations and leaf turgor pressure

Abstract

The aim of this work was to evaluate the potential of used sap flow (SF), trunk diameter variation (TDV) and leaf turgor (LT) sensors for assessing water stress in a `Arbequina¿ hedgerow olive orchard with 1667 trees ha-1. Measurements were made in control trees irrigated to replace 100% of the crop water needs, and in trees under two regulated deficit irrigation strategies, 60RDI and 30RDI, in which irrigation replaced ca. 60% and 30% of the control, respectively. From the SF and TDV measurements we calculated the daily difference, both for tree water consumption (DEp) and maximum trunk diameter (DMXTD), between RDI trees and control trees. With the LT sensors we recorded the leaf patch output pressure (Pp), which is related to the leaf turgor pressure. Both DEp and DMXTD responded quickly and markedly to changes in water stress. The seasonal dynamics of both indices agreed with that of the stem water potential. A decrease in the reliability of DEp was recorded on days of highly variable atmospheric demand. The LT sensors also showed to be highly sensitive to changes on water stress. Any of the three methods have a potential as indicators for precise irrigation in hedgerow olive orchards with high plant density and low soil water-holding capacity.